"We have them buckle up in our cars. It doesn't make sense not to have them buckle up elsewhere," she said.

So when a 2009 bill to require seat belts on school buses met opposition from Republican leaders and foundered, she decided to drive a school bus for the Ray Unified School District.

"In order to defuse their objection, I wanted to learn it from the ground up so that I would have firsthand knowledge," she said.

That experience informed SB 1115, McGuire's bill to require lap belts on all new school buses. Buses currently in school districts' fleets wouldn't be affected.

"We demand safety in all other aspects of our life - safety in working conditions, safety on our roads, with our own vehicles," she said. "It's time that we demand the same safety when it comes to the well-being of our children."

Out of office in 2011, McGuire got her commercial driver's license and drove a route through rural communities like Mammoth, sometimes covering 100 miles round trip.

Students of all ages rode her bus, from kindergartners to high school seniors. She said it became clear that lap belts would prevent them from slamming into the frame of the seat in front of them during a sudden stop.

"If they catch the frame, they're going to break a shoulder bone, a collarbone, they're going to knock teeth out, and they end up getting injured," McGuire said.

Seats in school buses are padded and close together, a safety technique called compartmentalization that, according to the National Highway Traffic Safety Administration, provides a safe enough environment on the bus without seat belts.

"There is no question that seat belts play an important role in keeping occupants safe in these vehicles, however school buses are different by design and use a different kind of safety restraint system that works extremely well," a NHTSA report reads.

Seat belts aren't required for buses heavier than 10,000 pounds, leaving school districts to decide whether they should be installed.

The Phoenix Union High School District has had lap belts in its buses for more than a decade, said Bryan Henderson, the district's transportation manager.

"There is no drawback to wearing a seat belt. Whereas, there may be a drawback to not wearing a seat belt," he said.

But Ron Latko, transportation director for Mesa Public Schools, said it would cost too much to install what he calls unnecessary seat belts on school buses.

"There are millions and millions of miles traveled every day with students in school buses," he said. "It's far safer than transporting them in your own personal car, seat belts or no seat belts."

Bob Riley, executive director of the National Association of State Directors of Pupil Transportation Systems, said lap-shoulder seat belts can add an extra element of safety during rollover accidents or side-on collisions, he said.

"Kids don't always sit with their hands on their laps facing forward completely in the seat," Riley said. "They hang out of the seat, they stand up, they kneel, they do all kinds of things while they're riding along and then if there's an accident they get none of the protection from the compartmentalization."

McGuire said that while she never had any major discipline issues with the students on her bus seat belts would encourage proper passenger behavior.

"It allows the driver to stay more focused on the road and the task at hand, which also contributes to the safety of the students on the bus," she said.

Her bill was assigned to the Senate Education Committee but has yet to be scheduled for a hearing. A similar bill she introduced last year wasn't heard in committee.

McGuire said might return to driving the bus when her service in the Legislature ends.

"It renewed my faith in young people today and their respect and their determination to become good adults," she said.